The recent appearance of the Acquired Immune Deficiency Syndrome is causing increasing concern. Exponential growth continues; 43 cases were recorded in 1980, 145 in 1981, 750 in 1982 and between 3 and 4 cases being seen daily in 1983. The central feature appears to be immunodeficiency, associated with the appearance, singly or together, of opportunistic infections, Kaposi's sarcoma and, more recently reported, a number of other neoplasms. The Syndrome was first identified among homosexual males and perhaps 80% of the cases are still being reported from among the gay community. However, the disease is also now being seen among heterosexual Haitian males, hemophiliacs treated with blood products, persons with drug dependency, heterosexual males in the general community and even among some women. It has been identified among recipients of blood transfusions and what may be a variant of the Syndrome has been reported among children not known to have intimate contact with AIDS patients. Cases have begun to be reported in other countries; for example, there appears to be an increasingly large number of case in Haiti. Despite much original and informative research by investigators in a variety of disciplines, the causes, pathogenesis, management and treatment remain poorly understood and incompletely resolved. Studies include diligent and original investigations in virology, immunology, clinical medicine, carcinogenesis, epidemiology, molecular biology. It is the Academy's experience that bringing together diverse information and investigators will assist in the necessary interdigitation of research efforts. Too, the problems are not only at a scientific interface, but one that includes social, behavioral and critical public health issues. The Conference program has been developed with input from key scientists in major institutions and agencies working on the problem; with very active studies under way, it is anticipated that these will be supplemented within the next months, with suitable modification of the program. We judge that there will be approximately one thousand participants at the meeting, the Conference Monograph will serve to disseminate what is currently known to an even wider audience.